Problems with perforated sheet metal cutting

[ClaudioK]

Problems with keeping the flame lit when cutting with 1 mm thick perforated steel sheet, 3 mm holes, 5 mm radius. When the cut feels vacuum, the cutting flame goes out and the cut is not completed. I increased the cutting speed from F7000 up to 10000, there are some improvements but it often stops again. Do you have any solution to keep the flame lit at least 1 second longer? The plasma is Hypertherm PowerMax Sync 65 automatic cut, with Fine Cut or 65A cartridge. Thank you

[jimcolt]

1. The THC should be off when cutting in expanded metal mode, and be sure the torch to work distance is at .125" (1/8").
2. Be sure your power supply is set in the "expanded metal mode.
3. If your cut speed is too slow expect occasional loss of arc. Try increasing cut speed to the point where cut quality is good, but arc remains on.

Jim Colt

[ClaudioK]

Many thanks, the THC is at speed 1 because I use Mach3 and with the THC off it seems to lose the active arc transfer confirmation part before triggering and starting the cut, resulting in the first part of the cut being skipped on the cutting path. Yes, I increased it up to F 10000 but I still haven't found cutting continuity, thanks for the reply.

[jimcolt]

You cannot use the expanded metal mode (on the plasma) to cut perforated metal with any success if the THC (height control) is on. The torch must be set at a fixed height and the THC off, and the plasma power sully needs to be set to expanded metal mode. The plasma senses when the arc goes into a hole and rapidly ramps the cutting arc down to a lower powered pilot arc. As soon as the plasma senses that it is back over the metal, the pilot arc ramps rapidly back up to cutting power. If the torch is travelling too slow the arc can extinguish when over the hole. If the THC is on expect the torch to dive towards the metal.

[weldguy]

I have had great success cutting expanded or perforated metal in the past, Jim's advice above is all you need once you get Mach sorted out. Maybe post your Mach 3 THC issue in the Mach 3 forum here https://www.plasmaspider.com/viewforum.php?f=55 and I am sure someone will be able to help you set that up differently so you can get success with your expanded cutting.

[ClaudioK]

Thanks for the replies, I removed the THC control by disabling the Csmio Fine Cut 45 Amper F8400 plugin, I made 6 cuts Ok then I started skipping the pieces again, I made a video. I will try increasing the speed from 8400 to around F9000. Thank you

[weldguy]

Just to confirm, do you have it in expanded metal mode?

Expanded.PNG (64.98 KiB) Viewed 752 times

[ClaudioK]

Yes, exactly, I used the button option above. However, the flame does not remain very active, (the technicians here tell me it must remain active for 3 seconds, this is not the case on my machine) I managed to cut around 600 pieces today.
Thanks for the replies

[tinspark]

If I had my rathers, I would have opted to shear them or have them sheared. It would not have taken more than 15 minutes to cut a sheet of perf with a shear with a a back gauge. I would bid it at a1/2 hour, and even at a shop rate of $100 per hour, I could charge $50 labor (not including materials) and feel like I made money.
If I opted to throw them on a plas. table, It would take me longer to go through them afterwards to remove the dross, not to mention the programming, cut time and consumable costs. seems like the hard way imho..
if curved or rounded parts, then that is a different story.

we had a bunch curved radius expanded metal to cut a while back (but the method below works with perf too) , and we laid a sheet of 24 gauge over the actual material (a sacrificial cover sheet over the job sheet) and sacrificed the thin sheet metal to save the labor of hand cutting or worrying about crashing by shutting off the THC as recommended above. when stuff warps it is no fun without THC, and can screw up a lot of metal. I have jacked up my fair share LOL!!
shearing all rectangle and square parts is typically the most efficient method for this type of stuff imho

[ClaudioK]

Yes, obviously there are other methods for cutting or shearing but Plasma is now functional, we are trying to find a solution as far as possible. The THC at speed 7 with the motors at speed 12000 and cutting at F8600 is the ideal setting for my machine with 25 mm recirculation screw and 20 mm for X which now cuts continuously. Even the Hypertherm consumable is still working after 1000 flame triggers. Thanks bye

[weldguy]

Glad to hear able to get your cutting done now. If you run into more trouble try turning OFF the THC, shouldn't have that on for perforated cutting in my experience.

[tinspark]

Yes, obviously there are other methods for cutting or shearing but Plasma is now functional, we are trying to find a solution as far as possible. The THC at speed 7 with the motors at speed 12000 and cutting at F8600 is the ideal setting for my machine with 25 mm recirculation screw and 20 mm for X which now cuts continuously. Even the Hypertherm consumable is still working after 1000 flame triggers. Thanks bye

[ClaudioK]

Very Thanks for response
Without THC I didn't recover, perhaps due to the imperfect planarity of the table on which the metal sheet rests